Going Solar at Northumberland Elementary School: A Proposition

After reviewing Northumberland School building power usage and costs, it is proposed that a solar array providing most of the power used by the Elementary school be considered. The following discussion frames that possibility.

The minimum month utilization over school year 13-14 was 78,000 kWh. Let’s shoot for an array that provides about 60,000 kWh per month, or well less than minimum usage. Net metering from Dominion will provide payback at the normal cost of power as long as power saved is less than total kWh actually used. Excess kWh’s provided back to the grid are compensated by Dominion at a much lower rate. Net savings with the proposed array are about $6,000/month. ($72,000/Year)

Assume that an array provides an average of 10 watts per square foot for 2000 hours per year. That is, every square foot provides 20 kWh/year. We need 720,000 kWh/year. That is we need 36,000 square feet to capture 360,000 watts, or 360 kilowatts. This will consume about an acre of space. Using a rule of thumb array cost of $3.00 per watt, investment would be about $1.1 million. Government rebates of 30% could reduce total investment by more than $300K and result in a payback time less than 10 years. Grants to support initial investment may be available. Most arrays are guaranteed for 20 to 30 years so that total power cost over 20 years is about half what it would have been with continued Dominion supply. That is, invest a million now, pay that back and save an additional million in the future. Of course increases in the power rate will not affect the base usage of 60,000 kWh provided by the array.

If this works, expansion to a second array for the Middle and High School could also make sense. That could save another $2 million if implemented for all schools.

FYI & consideration. We certainly get more sun than NJ, NY and New England where this is being done. Should we look at a 3rd-party financing source and possible providers and run the real economics? Are we in contact with the National Solar Schools Consortium?

This could: